1. Field of the Invention
This invention relates to a process of decolorizing pulp and paper mill wastewater and, more specifically, to a process for treating wastewater effluent from a pulp or paper mill with a novel microorganism of the strain Pseudomonas aeruginosa whereby color bodies in the pulp and paper wastewater are thereby removed and the wastewater is decolorized.
2. Description of the Prior Art
Pulp and paper mill wastewaters are generally obtained as a result of manufacturing processes for the preparation of wood pulp and paper. Due to the presence of organic and inorganic materials in such wastewaters rendering such wastewaters unsuitable for reuse and undesirable for release into the biosphere due to the pollution problems which result when they are discharged untreated, pulp and paper mill wastewaters are generally processed in biological treatment systems, for example, aerated lagoons or activated sludge systems, for removal of biodegradable organic matter prior to reuse or discharge to receiving bodies of water.
While the biological processes occurring during such a biological treatment provide the ability to produce effluent which has both low biological oxygen demand (BOD) and low chemical oxygen demand (COD), unfortunately, conventionally employed biological treatment systems accomplish very little, if any, reduction in color of the pulp and paper mill wastewater when the pulp and paper wastewater is so treated. for example, trickling filters have been recommended by governmental environmental regulatory agencies for use in processing wastewater effluent from pulp and paper mills. However, no color removal has been achieved (see H. T. Chen et al., "Four Biological Systems for Treating Integrated Paper Mill Effluent," TAPPI, 57, 5 (11-115) (1974)).
Also, a system comprising plastic disks on a single shaft which is rotated (as disclosed in D. J. Bennett et al., "Pilot Application of the Rotating Biological Surface Concept for Secondary Treatment of Insulating Board Mill Effluents," TAPPI, 56, 12 (182-187) (1973) and an activated sludge treatment using oxygen instead of air (as disclosed in R. J. Grader et al., "The Activated Sludge Process Using High-Purity for Treating Kraft Mill Wastewater," TAPPI, 56, 4 (103-107) (1973)) have been used, but no reduction in color of paper mill waste has been reported using either system. In some instances, it has been observed that an increase in true color in actuality occurs.
From this observed result, it is apparent that the aerobic bacteria typically present in such treatment systems are not capable of utilizing the color bodies which are present in the wastewater from pulp and paper processing as a source of food. Even with the well-known ability and adaptability of bacteria to adjust to and utilize new substrates as food sources, thus far the development of bacteria capable of reducing color in pulp and paper mill wastewater effluent has not been reported.
Whereas regulatory guidelines for paper mill waste color have not been set forth, much work has been done to evaluate the various physical-chemical methods for removing color, such as lime precipitation, resin separation, activated carbon adsorption, and ozonation, all with varied degrees of success and in all cases involving high cost for initial capital equipment and ongoing operating and maintenance expenditures. Refer to review article for chemical physical methods, "Current Status of the Effluent Decolorization Problem," by Isiah Gellman and Herbert F. Berger. TAPPI, volume 57, No. 9 (September 1974).
With the increasing concern as to minimization of the problems arising from pollution, biological processes utilizing microorganisms are being industrially employed in an increasing amount, and a large amount of activity in research and development is occurring presently to develop new microbial strains capable of use in wastewater treatment both industrially and domestically. Even with this increased activity in investigating and developing strains of microorganisms to solve particular waste removal problems, no reduction in color which exists in effluent wastewater from pulp and paper mills has been achieved.
In the past, Polyporus versicolor has been used to degrade color bodies in paper mill effluent, but such was in the presence of carbohydrates. However, no significant reduction was seen in the absence of carbohydrates (e.g., as disclosed in Marton and Stern, "Decolorization of Kraft Black Liquor with Polyporus versicolor, a White Fungus," TAPPI, 52, 10 (1969)). Furthermore, filamentous organisms such as Polyporus versicolor are impractical for use in biological treatment systems.